Sorting device for separating articles of different conductivities



A ril 19, 1949.

c T. PARKER 2,467,773

SORTING DEVICE FOR SEPARATING ARTICLES OF DIFFERENT CONDUCTIVITIES Filed May 11, 1945 INVENTOR.

WITNESS. 4s

Patented Apr. 19, 1949 SORTING DEVICE FOR SEPARATING ARTI- CLES DIFFERENT CONDUCTIVITIES h r cs, '1?- Park Mo 1. .1., as i or to ere av corporation of, 1111- & Company, Moline,

nois

Application May 111;, 1945, SerialNo. 593,187

11, Claims.

The presentnvention r lates gen r l y to sorting; devices and hasfor. its principal object the p ovision of a s rtin de iceor aut mat ca separating stones from crops, with particular ref rence. t r otr pswhi hare. du out. f he 1 ground by means of av scoop- 01: plow, together with a considerable. quantity of dirt and stones,

invention is particularly Well adaptedto harvesting potatoes, although I do not intend its use to be limited to this particular crop. f r theprinip es of my inve t on; may be applied t o er root crops, such as beets.

It. is well kn wn. othose skill d. in the art that potatoes can be easily sep rated from. any soil tending to cling thereto, but. heretofore no 1 mechanism has, been devised: which will automatically and satisfactorily s parate potatoes. from stones of a similar size, and shape. Consequently, commercial potato harvesters available on the market today merely ai-gitatev the. potatoes toseparate the soil therefrom and then discharge the. potatoes and stonesin, a windrowv behind the harvester to be g ed at r by hand.

Therefore, it is a more specific object of my invention to provide. a. testing device which is sensitive to certain; if erences etween p toes and stones, and separating mechanism controlled by the testing device for mechanically performing the, separation,

In the. accomplishment of these obje t I have recognized two important. differences be tween potatoes and" stones of, a; similar size, first, that the surfaces of potatoes can be penetrated byasharp instrument, and'second, that. the electrical conductivity of' a potato is. greater than that of a stone. Hence, by slightly piercing or penetrating the surface of each potato with a suitable testing instrument, an electrical contact can be made for thepurpose of passing a current a through the potato. However, when the same instrument is applied to. a stone with an equal pressure, it obviously will not penetrate the surface and furthermore, since the electrical conductivity of the stone is verylow a considerably smaller current will flow through the testing device and the stone fora given voltage applied thereto. According to the present invention, this difference in electrical resistance is used to control a separating mechanism such as; a trap door t icart. after a consid r iono the f low ng, e-

scription, in which reference is had to the drawings appended hereto, in which Figure 1 is a sectional elevational, view taken along the. center line of a conveyor equipped, with a sorting device embodyin the Principles of my invention, showing in diagrammatical form the electrical circuits involved;

Figure 21s a similar view showing a, modified form of my invention; and

Figure 3 is a top plan View of a conveyor showing a third embodiment of my invention.

Referring now to. the drawings, and more par icularly to Figure l. the conveyor comprises a, trough 5 havingv an inclinedbottom 6 and a pair of laterally spaced side walls '1, between which is; disposed an endless chain type conveyor 8 having transversely disposed slats 8| movable along the trough 5m a downward direction as indica ed by the arrow. The. trap door is pivotally mounted, on a transverse pivot ID in the bottom of the ou h 5 and is swinsab e e t al y ab ut the transverse axis, Ill from a normal position in alignment with the bottom 6 of the trough downwardly away from. an, opening H in the bottom wall 6. The trap door 9 is held in closed position by meansof a, pair of toggle links l2 having their adjacent ends pivotally connected together by a pivot pin I3. The outer end of one of the links is pivoted at M to the bottom of the trap door 9, and the other link l2 ispivotally connected at IE to any suitable stationary support It, which may be a part of the supporting frame of the conveyor. The tension spring I1 is connected to the pivot l3 interconnecting the links [2 and is anchored to any suitable stationary support l8, and is stressed in tension to urge the toggle links [2 in alignment, supporting the trap door in its closed. position as determined by a stop I9 on the door 9 extending under the edge of the trough bottom 6'.

The trap door is opened by means of a solenoid coil 25 having an armature 26 connected to the interconnecting pivot IS on the side opposite the spring ll. When the solenoid coil 25 is energized, the armature 26' pulls the pivot l3 toward the left against the tension of the spring ll, thereby opening the trap door 9 downwardly away from the floor opening H.

The solenoid coil 25 is energized from any suitable source of electric energy at substantially constant voltage, such as a battery 21, one side of the latter being connected by a conductor 28 to one side of the solenoid coil l5, while the other side of the battery is connected through a relay 255 with the other sideof' the coil 25. The contacts of the relay 29 are normally open, permitting the spring acting through the toggle links l2, to hold the trap door 9 in closed position.

The potatoes are distinguished from the stones by means of a testing device indicated in its entirety by reference numeral 35 and comprising a contact wheel 36 journaled on an axle 31, which is fixed to a supporting arm 38. The arm 38 is journaled in a support 39 fixed to the outer side of the conveyor trough by means of bolts 40. The support 39 is insulated from the conveyor trough and the bolts 49 are provided with insulating washers 4|, thereby completely insulating the support 39 from the conveyor in a manner well known to those skilled in the art. The contact wheel 36 is supported over the bottom 6 of the trough 5 and is rotatable about a transverse axis and also is swingable vertically relative to the trough 5 about a transverse axis. A stop lug 42 on the support 39 engages the supporting arm 38 to prevent the wheel 36 from touching the bottom 6 of the trough.

The contact wheel 36 is provided with a series of circumferentially spaced contact teeth which are adapted to penetrate the surfaces of the potatoes to establish a good electrical contact between the wheel 36 and the potatoes, but it is preferable that the teeth 43 be made as short as possible in order that no appreciable damage would be done to the potatoes. Possibly, if the potatoes are cleaned, it would not be necessary to provide teeth on the contact wheel, but in order to insure a good contact under all conditions the contact teeth are included. It is believed that a series of rasps such as are found on files, will serve the purpose, or if desired, teeth may be provided in the nature of sawteeth.

Another series of teeth 44 is provided on the surface of the trap door 9, and the contact wheel 36 is positioned substantially directly above the trap door 9 but spaced above the latter a distance slightly less than the diameter of the smaller potatoes to be handled.

One side of the coil 45 of the relay 29 is connected to the battery 21 while the other side is connected in series with a variable resistor 46 to a connection 41 with the conveyor trough bottom 6. A wire 48 is connected to the wire 28 on the other side of the battery and to the contact wheel 36 through the supporting arms 38.

During operation, the conveyor chain 8 moves toward the right as viewed in Figure 1, the slats 9 engaging the stones and potatoes and moving them between the contact wheel 36 on the trap door 9. The wheel 36 rolls over the stones and potatoes, making an electrical contact with each stone and each potato. However, since the teeth do not penetrate the surfaces of the stones, there is very little area of contact between the points of the teeth 43 and the stones. Furthermore, the electrical conductivity of stone is very low and therefore substantially no current flows through a stone between the trap door 9 and the contact wheel 36 unless the stone is wet, in which case a very small current will flow between the teeth 43, 44 along the wet surface of the stone. In any case however the current through the control circuit, which includes the solenoid coil 45, the variable resistor 46 and the contact wheel 36 is insufilcient to cause the solenoid coil 45 to close the relay 29, therefore the trap door 9 remains closed and the stones are conveyed along the conveyor trough 5.

When a potato passes under the contact wheel 36, however, the teeth 43, 44 slightly penetrate the surface of the potato, establishing a good electrical contact, and since the conductivity of a potato is appreciably greater than that of a stone, a current will flow through the solenoid coil 45, the variable resistor 46, the bottom 6 and the trap door 9 in the conveyor, the contact wheel 36, its supporting arm 38, and returning to the battery through the wires 48 and 28. This current, flowing through the solenoid coil 45 is suflicient to close the relay 29, thereby energizing the solenoid coil 25, collapsing the toggle links l2 and thus opening the trap door 9, whereupon the potato drops through the opening H to any suitable collector (not shown) beneath the conveyor trough 5.

The coil 45 is obviously designed to close the relay responsive to the flow of the small current which will be transmitted through the potato. Inasmuch as the resistance of the potatoes will vary according to moisture content and other conditions, the variable resistor 46 is provided for the purpose of adjustin the current flow through the coil 45 to the proper value, and also to insure that the current which flows between the contact teeth 43, 44 over the surface of the wet stone is limited to a value beneath the minimum required for closing the relay 29.

As the trap door 9 swings downwardly, the potato drops away from contact with the wheel 36, the downward movement of which is limited by the stop 42, breaking the circuit through the coil 45 and deenergizing the solenoid coil 25. The weight of the potato however is suflicient to overcome the tension of the light spring until the potato falls away from the trap door 9, after which the spring I! quickly restores the door to closed position. With the toggle links l2 in substantially dead-center alignment, the weight of the stones is ineffective to open the door 9 without assistance from the solenoid coil 25.

In the embodiment of Figure 2, the stones are dropped through the trap door opening while the potatoes are conducted downwardly along the conveyor trough 5. In this embodiment, the trap door 9 is provided with a lever arm 5|) rigidly fixed to the bottom of the door 9 and extending downwardly therefrom. The solenoid coil 5| is provided with an armature 52 which is pivotally connected at 53 and the trap door 9 is held in closed position as long as the solenoid coil 5| is energized, but when the coil is deenergized the weight of the door 9 plus the weight of a stone carried thereon is suificient to quickly cause the door to drop away from the opening allowing the stone to drop through the latter. One side of the solenoid coil 5| is connected by a wire 54 to one side of the battery 2'! and the other side of the coil 5| is connected through a realy 55 with the other side of the battery 21. Since this is a normally closed connection, a disconnect switch 56 is provided between the relay 55 and the battery 21, The relay 55 is normally held closed by a relay coil 51 one end of which is connected to the wire 58 connecting the relay 55 with the switch 56. The other end of the relay 5'! is connected in series with a variable resistor 46 to the wheel supporting arm 38 by a wire 59.

In this embodiment the wheel supporting arm 38 is provided with a contact arm 60 which carries the contact 6| which is normally in contact with a stationary contact 62, the latter being connected by a wire 63 to the battery 27. Thus, there is a. normally closed circuit through the relay coil 51, the resistor 46, arm 60, and contacts 6|, '62, which hold the relay 55 in closed position ama s 5.- and thereby constantly energizing. the. solenoid coil 5.1 to hold the trapdoo-r fltclosed...

. When either. a stone ora. potato: moves. underv the. contact. wheel. 3.5, the latter is. raised. about. its. pivotal. connection.- 39 with. the. support. 39. a clockwise. direction. This. movement, swings. the arm. 6.0. and contact 6.1.- away from the star tionary. contact 62, and in the case of a stone, this. breaks the circuit. through the. relay coil 51'; and allows. the. relay to open and deenerglzei thesolenoid coil 5!. This. allows. the trap door. 9*. tn. drop open,.dis.chargi-ng. the stone beneaththe; conveyor. (L As the stone drops. away from the; wheel 36. the latter returns. by gravity. into. the position. limited by the. stop lug 42,. thereby re'-- closing. the. contacts 61., 6.2. and. establishing. the circuit. throughrthev relay coil. 5.1.. The. relay: 55 then. closes and energizes thesolenoid 5!. which. closes. the trap door 9. When a potato passes. under the contact. wheel the. contacts. 6.1, 62 are, separated as when astone is. engagedby the. wheel; but in this case. a. parallel. circuit. is established. throughthe armtli, the .wheel 36, the teeth 43, 4.4,, and. a. connection. between. the, bottom 6 of; the conveyor and the wire 54 which returns to. the. battery 21. Hence, this. parallel. circuit by passes the contacts 6.1 62. andv thereby holds the. relay 55 closed when. a. potato. passes under the. wheel 36,. with the result that. the. potato is not, discharged through the opening H but iscarried. on along the conveyor trough 5. It willbe noted. that a second variable resistor 66. connected in series with the. contacts GI, 62 in. order to. ad- Jlust. the. resistance of the. circuit through the contacts. 6|, 62 to a value substantially equal. to the resistance. of the potatoes between the teeth 43,. 4.4.. It is possible that under some crop conditions the current flowing through the crops. betweenthe contact teeth 53, 44 may be insulficient to operate. the relay 29 or 55. which energizes the. solenoid coil 25 or 5|,respectively, in which case. it is believed that anyone skilled in the art can. interpose suitable means for amplifying the current through the crops. to operate the relay.

' In the embodiment shown in Figure 3, a differerit type of separating, means has been provided. in place of the trap door 9 in. Figures 1. and'.2.. In Figure 3, the stones are discharged through a. laterally extending chute Ill by means of, animpeller II in a form of an arm which is pivotally mounted on. a vertical pivot pin 12, thelatter beinggfirmly supported on a stationary frame memher-l3. The impeller "H is provided with a stone engaging member M which projects through an opening 1.5 in the side wall T of the conveyor trough 5 on. the side opposite the chute l0. Thus, when the arm H is swung about its pivot 12 in a counterclockwise direction, the engaging meme her 14 projects transversely across the trough 5'. and drives the stone laterally over the chut Ill. The impeller arm H is actuated by means of a strong compression. spring 16 which'bears. against thearm TI and. reacts against a suitable sta tionary' support Tl.

Normally, the arm is retained in a position in. which the stone engaging part M is retracted from the conveyor trough 5. This is accomplished. by means of a latch 13 pivotally mounted on a pivot pin 19 and having a latch dog which engages the outer end of the arm H. The latch arm 18 is provided with a crank arm 8!, to. which is connected a tension spring 82 anchored to a stationary support 83. The spring 82 is biased. to: hold the latch dog BB in latched. position, but is yieldable to permit. the disengagement. of. the

6;. latchdog, 8.0.;v thereby permitting the. compression: spring 16 to forcefully project the stone. 9131-? gaging member 14 across the bottom 6 ofthe-conveyortddrivethe stone; over the chute 1.0.. The member. 1.4, is retracted. by swinging the-arm. ll. in a; clockwise direction; about its pivot support. l2 toirelatch latch dog. 80, this being, accom. plishedbymeans of. a resetting cam 85. fixed. to. a, continuously. rotating. shaft 86 which rotates lira-counter: clockwise direction as indicated by the; arrows. The: arm ll isprovided with anex tension 8]. beyond the. pivot 12, which is. moved intathepath of. movement of, the cam v when the impeller H. is: actuated. to-engage a stone. The; can 85 then engages the extension therebn swinging. the; arm, in. a. clockwise direction about thepivot. 1.2 to compress the spring 16 and reset the. latch 8.0.. The. shaft 86. is continuously ro tated. any suitable; driving means, the. details or which are-not animportant. part of the present.

invention.

The-latchdog-tll isytripped by means. oi a sole-. noidi coil 9.0;.havingan. armature. 9lconnected to the crankarm. 8|... One. end; of the solenoid. coil 9.11 is connected through a variable resistor 92 and a relay 93 to one side of the battery 21. Theother. side- 02 the. solenoid coil 9.0; is connected.- to arstationary contact 94. whlchisengageable with amovable: contact 95v mounted. on an arm. 96 which. extends upwardly from a rockshaft. 3 9 on. which. the contact wheel. supporting arm 38. is mounted. The. rockshaft 39! is. connected. to they batteryrby awire 91...

Normally. the contactsv a4, 95- are separated,

but when. either a potatoor a. stone travels. under the Wheel. 36. raising, thelatten. the rockshaft 39' is. rotated about ltstransverse axis to close the.- contacts 94,.95ithereby closing the. circuit through. the solenoid coil 941 andtripm'ngv the latch dog 80. tripping operation. is prevented, however,

when. a, potatocontacts the-wheel. 3.55, by opening.

relay 93. atv the same time that the contacts 94., 9.5 are; closed. The. relay 93. is a normally. closedrelay having an operatingcoil lilll, one. side. of; which is. connected to. one side of the. battery andthe-other side. of which is connected through avariable resistorllll. to the. conveyor trough 5.. When the contact: wheel. 36. engages a potato, a circuit is. completed. through. the relay Hit, the variable. resistor. lllli, the. conveyor trough 5, the. potato, thewheel. 36,. the supporting arm- 55, the rockshait. 393,. and. the, wire. 91,. which energizes. therelay coil. m0 toopen. the. relay. stand therelint-- preventing the solenoid so. from being enersized As. indicated. by the arrow, the. conveyor 8. moves toward. the left in this. embodiment, cartying: the. stones and. potatoes under the wheel 36., which makes. contact with each. stone and. potato successively; The latch. dog 8.8. remains. latched. under. the. arm. U until. the solenoid coil. an. is energizedto trip. the latch, which. happens when. a. stone: raises the. wheel 36,. closing the. contacts 294., 95,.buthaving. an. electrical. resistance high enough. to. prevent. the relay coil Ill!)v from opening the relay contact 93.. It. will be. noted that; the. contact wheel 3.5 is positioned slightly ahead of. the stone engaging member 14, for the stone will be moved slightly beyond. the wheel 35 by, the. time. the. arm ll. swings. the member 14. acrossthe conveyor trough 5. to engage the stone,

Other embodiments of. my invention will now. be apparent.tothoseskilled in the art and therefore I. dov not. intend my invention tolbev limited to. the particular. details shown and described 7 herein except as set forth in the claims which follow.

I claim:

1. A sorting device for separating articles of different conductivities, comprising a passageway along which the articles are conducted, a contact wheel mounted in said passageway by means providing for movement relative thereto, said wheel being shifted by engagement with each of said articles as the latter pass thereby, separating mechanism for acting selectively upon said articles to separate one from another, an electric circuit for governing the actuation of said separating mechanism, said circuit including switching means actuated by shifting movement of said contact wheel for controlling current flow in said circuit, said wheel having means for penetrating the surfaces of certain of the articles for establishing a good electrical contact, said penetrating means being incapable of penetrating the surfaces of others of said articles, whereby the electrical resistance in said circuit is increased, and means responsive to a predetermined amount of current through said electrical contact for influencing the control of said separating mechanism.

2. A sorting device for separating root crops from stones comprising a passageway through which the crops and stones are conducted, a contact member supported in said passageway by means providing for movement relative thereto, said member being shifted by engagement with each stone or crop root as the latter pass thereby, separating mechanism for acting upon said stones and root crops to separate one from another, an electric circuit for governing the actuation of said separating mechanism, said circuit including switching means actuated by shifting movement of said contact member to close said circuit to effect an actuation of said separating mechanism, said contact member having means for penetrating the surfaces of the root crops for establishing a good electrical contact therewith, said penetrating means being incapable of penetrating the surface of the stones, whereby the electrical resistance in said circuit is increased, and means responsive to flow of current through said electrical contact for breaking said circuit.

3. A sorting device for separating root crops from stones comprising a passageway through which the crops and stones are conducted, a contact member supported in said passageway by means providing for movement relative thereto, said member being shifted by engagement with each stone or crop root as the latter pass thereby, separating mechanism for acting upon said stones and root crops to separate one from another, an electric circuit for governing the actuation of said separating mechanism, said circuit including normally closed switching means for closing said circuit to hold said separating mechanism in one position, said switching means being opened by shifting movement of said contact member to release said mechanism, said contact member having means for penetrating the surfaces of the root crops for establishing a good electrical contact therewith, said penetrating means being incapable of penetrating the surfaces of the stones, whereby the electrical resistance in said circuit is increased, and means responsive to flow of current through said electrical contact for closing said circuit independent of said switching means.

4. A sorting device for separating root crops from stones comprising a passageway through which the crops and stones are conducted, a contact member supported in said passageway providing for movement relative thereto, said memher being shifted by engagement with each stone or crop root as the latter pass thereby, a trap door in said passageway through which stones can pass, electrically energized means for normally holding said door in closed position including an electric circuit comprising normally closed switching means adapted to be opened by shifting movement of said contact member to release the trap door to pass a stone, said contact member having means establishing electrical contact with each stone and crop root, successively, said electrical contact strongly established with root crops by penetrating means on said contact member, said penetrating means being incapable of penetrating surfaces of stones to obtain a good electrical contact, and said contact member electrically connected with said door holding means to energize the latter through contact with a crop root. thereby holding said trap door closed to prevent crops from passing therethrough.

5. A sorting device for separating root crops from stones comprising a passageway through which the crops and stones are conducted, a con tact wheel rotatably supported in said passageway providing for movement relative thereto, said wheel being shifted by engagement with each stone and crop root as the latter pass thereby, a trap door in said passageway through which stones can pass, means including a solenoid coil for normally holding said door in closed position, a source of electrical energy, and a relay connecting said source with said coil, normally closed switching means associated with said contact wheel for controlling said relay to energize said solenoid coil, said switching means being opened by said movement of the wheel when the latter engages stones and crops, said contact Wheel having means establishing a circuit through the crops and stones in parallel with said switching means to control said relay independent of said switching means.

6. A sorting device for separating articles of different conductivities, comprising a passageway along which the articles are conducted, a contact member supported in said passageway by means providing for movement relative thereto, said member being shifted by engagement with each of said articles as the latter pass thereby, separating mechanism for acting selectively upon said articles to separate one from another, electric circuit means for operating said separating mechanism, said circuit means including switching means actuated by shifting movement of said contact member for interrupting a flow of current to allow said separating means to move from one position to another, said contact member having means contacting each of said articles, successively, and means responsive to flow of current through said contacting means for restoring said flow of current to prevent said separating means from moving from said one position to the other.

'7. A sorting device for separating articles of different conductivities, comprising a passageway along which the articles are conducted, a contact member supported in said passageway by means providing for movement relative thereto, said member being shifted by engagement with each of said articles as the latter pass thereby, separating mechanism for acting selectively upon said articles to separate one from another, electric circuit means for operating said separating mechanism, said circuit means actuated by shifting movement of said contact member for estab-' lishing a flow of current to initiate a movement of said separating means, said contact member having means for electrically contacting each of said articles, successively, said contact member having means for penetrating the surfaces of the articles of greater conductivity, said penetrating means being incapable of penetrating the surfaces of the articles of the lesser conductivity, whereby the electrical resistance in said circuit is greatly increased, and means responsive to flow of current through said contacting means for interrupting said flow of current to prevent said initiation of movement of the separating means.

8. A sorting device for separating root crops from stones comprising a passageway through which the crops and stones are conducted, a contact member supported in said passageway by means providing for movement relative thereto, said member being shifted by engagement with each stone or crop root as the latter pass thereby, separating mechanism for acting upon said stones and root crops to separate one from another, an electric circuit for governing the actuation of said separating mechanism, said circuit including switching means closed by said movement of said contact member to initiate a movement of said separating means, said contact member having means establishing electrical contact with each stone and crop root, successively, said electrical contact strongly established with root crops by penetrating means on said contact member, said penetrating means being incapable of penetrating surfaces of stones to obtain a good electrical contact therewith, and a relay having an operating coil connected with said contact means to receive energy therethrough in appreciably greater amount when contact is made with crops than when contact is made with stones, said relay being actuated by said greater amount of energy only, and including normally closed switching means in series with said first mentioned switching means for preventing the initiating of movement of said separating means when contact is made with crops but permitting said movement when contact is made with stones.

9. A sorting device for separating root crops from stones comprising a passageway through which the crops and stones are conducted, a contact member supported in said passageway by means providing for movement relative thereto, said member being shifted by engagement with each stone and crop root as the latter pass thereby, stone impelling means engageable with stones in said passageway for separating the stones from the crops, a tripping device for initiating movement of said impelling means, control means responsive to shifting movement of said contact member for actuating said tripping device, said contact member having means establishing electrical contact with each stone and crop root, successively, for transmitting current therethrough, said electrical contact strongly established with root crops by penetrating means on said contact member, said penetrating means being incapable of penetrating surfaces of stones to obtain a good contact therewith, and means responsive to a predetermined minimum flow of current through said contact for preventing the tripping of said device.

10. The combination set forth in claim 9 including the further provision that said impelling means comprises a pivoted arm biased for movement into engagement with stones in said passageway, and said tripping device comprises a latch engageable with said arm for holding the latter out of said passageway against the pressure of said biasing means, and power driven means for returning said arm to latched position after said device has been tripped.

11. The combination set forth in claim 9, including the further provision of an electric citcuit including said contact establishing means, a source of electrical energy, and means for adjusting the resistance of said circuit to produce a current greater than said minimum value when said contact member contacts crops in said passageway and a current less than said minimum value when said member contacts stones in said passageway.

CHARLES T. PARKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,153,381 Gudmundsen Sept. 14, 1915 1,431,814 Kanengieter Oct. 10, 1922 1,967,296 Dixon July 24, 1934 1,987,244 Moore Jan. 8, 1935 2,086,060 Appleyard July 6, 1937 2,101,381 Appleyard Dec. 7, 1937 2,198,285 Krenzer Apr. 23, 1940 FOREIGN PATENTS Number Country Date 494,092 Germany May 7, 1930 

